variable declaration within the while loop C/C++

Question

according to me following while loop should be infinite but it runs only thrice

   main()
   {
   int i=3;       
   while(i--)
    {
      int i=100;
      i--;
      printf("%d..",i);
    }
   }

it outputs 99..99..99

but according to me it should run infinite times as every time control enters while loop it gets value 100.so it will never reach zero. just to experiment i replaced int i=100; with i=100; in side the while loop and now it runs infinite times..WHY???

Answer 1

The variable i in while(i--) is different from the variable i defined inside the loop.

Basically int i = 100 shadows the previous int i = 3 and inside the block of the while you're referring to a new variable.

At the end of the day, I find no plausible scenario where you would need to do something like this.